Mechanical hammer



July 15, 1930. H. NIELSEN 1,770,656

MECHANICAL HAMMER Filed March so, 1928 2 Sheets-Sheet 1 II [I IIHG'Z I 'll July 15, 1930. H. NIELSEN 1,770,656

MECHANICAL HAMMER Filed March 50, 1928 2 Sheets-Sheet 2 Patented July 15,- 1930 UNITED STATES HERMAN NIELSEN, OF FREDERIKSBERG, IBY COPENHAGEN, DENMARK MECHANICAL HAMMER Application filed March 30, 1928, Serial No. 266,085, and in Denmark February 18, 1928.

The present invention relates to a mechanical hammer which is adapted for chiselling, stamping, caulking, riveting and like operations, is partly intended to act as a substitute for the known pneumatic tool and, more particularly, is suited for use in trades and the smaller industries.

The hammer of the present invention is of the kind in which a striker block is pivotally connected to a revoluble body and, under action of the centrifugal force at each revolution of the said body, is flung against the tool, for example, a chisel, a button set, a caulking tool or the like. According to the present invention there is associated with the revoluble body a locking device, for instance a pawl which, under the action of a spring,

if need be, automatically catches and retains the striker block as the latter rebounds from impact on the tool but, under the influence of a stop or the like, which is adjustable but not rotatable in relation to the casing of the hammer, automatically releases the striker block when the latter has passed the tool. lVhen the striker block is released by said lock it is flung by the centrifugal force into striking position and the moment of release in each revolution of the spindle carrying the revoluble body is preferably chosen so as to secure optimum impact. Release of the lock can take place automatically while the hammer is in use. For example, in a portable hammer, the operator, while holding the handle of the hammer, involuntarily actu ates a press button or a lever which is thereby depressed. If the operator lets go the handle of the hammer, or if he intentionally relieves his pressure on the said press button or lever the latter will, it may be under action of a 4 spring, move so as to prevent release of the aforesaid lock, and the striker block will, therefore, be locked in an inoperative position even though it still continues to participate in the rotation of the spindle. With 4 stationary hammers or the li e the release of the lock may be operated from the starting device or independently. The striker block is arranged in a body attached to or integral with a revolving spindle and has such a form that the center of gravity common to block will transfer to the latter its kinetic energy, as the percussion center of the striker block is located in the line of impact. The shock due to impact has not therefore to be taken up by the bearings which support the spindle, and only a minimum of vibration is transmitted to the casing enclosing the ham mer, and to the handle associated therewith. When the hammer according to the present invention is used as a tradesmans tool the spindle is coupled to a motor by means of a flexible shaft the elasticity of which is utilized to impart to the striker block the maximum possible velocity at the moment of impact. At the moment when the striker block strikes the tool it loses its velocity and it must therefore receive a large amount of energy while it is being accelerated. Such acceleration cannot take place suddenly and therefore a certain amount of energy is accumulated in the flexible shaft by the twisting oi. the same. This torsion produces the effect of a spring which first accumulates a part of the energy of the driving motor and thereafter delivers such energy to the striker block during the remainder of the revolution, so that the velocity of the block will be continuously increasing between each two successive blows from nil to the maximum. As the amount of energy transferred by a blow is proportional to the second power of the relative velocities of the impacting parts, it is possible, by employing a flexible shaft of suitable elasticity, to obtain a considerable increase in the force of hammer, since the velocity of striker block at the moment of impact considerably exceeds the speed of the driving motor.

If a flexible shaft isnot used for transmitting the motion from the driving motor to the hammer, for example with stationary hammers, an elastic intermediate member may be inter osed between the motor and the hammer, y means of which a similar object is achieved.

In the accompanying drawing a constructional form of the invention has been exemplified, in which i Fig. 1 is a bench hammer seen in section along the line I-I in Fig. 2.

Fig. 2 is a. sectional view along the line II--II in Fig. 1,

Fig. 3 is the striking block in section along the line III-III in Fig. 1, in free position,

Fig. 4 is the same view with the striking block in locked posit-ion,

Fig. 5 is the member which effects the releasing of the lock that holds the striking block, in end view.

The hammer comprises an outer casing 1 which is continued in a handle 2 and a barrel 3 into which latter a suitable tool 4 may be inserted, for example a chisel, button set or the like. In the casing 1 are provided two ball bearings 5 in which is journalled a body 6. This has at its one end a pin 7 which is coupled to a flexible shaft 8 by means of a sleeve coupling 9 so that the bod 6 is caused to revolve with the flexible sha t 8. In the body 6 is mounted an eccentric pin 10 which is parallel to the axis of rotation of body 6. On this pin 10 is pivotally mounted a striker block 11 which, at its rear, has a lug 12, adapted when the striker block has been swung out into the striking position shown in Fig. 2, to bear against the body 6. The striker block 11 has, as shown in Figs. 3 and 4 a recess 13 in its one side; this recess is situated between a lug 14 and a bevel or inclined surface 15. The part of body 6 which is journalled in the ball bearing 5 to the left in Fig. 1 has a slot-like hole in which there is disposed a double armed pawl 16 pivoted on a pin 17 mounted in the body 6. The pawl 16 is under action of a spring 18 which tends to turn it counterclockwise (Fig. 1). The one arm of pawl 16 has a nose 19 which projects into the recess 13 in the striker block 11, (see Fig. 4) when the same is in the inoperative or locked position, and the lug 14 on the striking block engages over the nose 19 of the pawl so that the said block cannot, under action of the centrifugal force, be slung out into the position shown in Figs. 2 and 3.

The other arm 20 of pawl 16 projects into as ace 21 in the casing 1 and there coacts wit a stop 22 on a cylindrical body 23 which can be moved backwards and forwards in a bore or cavity 24 in casing 1. In the one limb of the handle 2 is arranged a double armed lever 25 which is under the influence of a spring 27 located in a hole bored in casing 1. The lower end of lever 25 terminates in a pin 28 projecting into a hole in the bod 23 so that an oscillation of lever 25 will shi t the body 23 while, at the same time, the lever prevents this body from turning. In the space 29 recessed into the handle 2 is disposed a lever 30 pivoting on a pin 31., The lever 30 is connected through a push rod 32 with the lever 25 so that the latter is rotated when the lever 30 is depressed into the recess 29.

The striker block 11 is recessed as at 33, and one wall 34 of the recess forms the peen of a hammer with which the striker block strikes the tool 4 at each revolution.

The operation of the hammer is as follows:

Assuming the striking block 11 to be locked by the pawl 16 owing to the extension 19 of the latter engaging, as shown in Fig. 4, in recess 13 in said block 11, the latter will remain in locked position even after the flexible shaft 8 and with it body 6 has started to rotate. When, after directing the tool 4 against the work, the operator depresses the lever 30 the movement of this lever will be transmitted through the push rod 32 and lever 25, to body 23 which is thus caused to slide to the right (Fig. 1). The stop 22 will then move into the path of the rear end 20 of pawl 16 and as the latter is carried round with the body 6 the said stop, acting on the pawl, will so tilt the latter that the nose 19 releases the lug 14 at that point of rotation of body 6 when the striker block has just passed the tool 4. After this has happened the striker block will be flung b the centrifugal force, from the osition s own in Fig. 4 to that shown in Fig. 3 and it remains in this position until it strikes the tool 4. After this has occurred the striker block 11 is forced around the pin 10 towards the body 6 and is there caught afresh by the pawl 16 the lug 14 pushing the nose 19 inwards whereby the spring 18 is compressed and when the lug 14 has passed the nose 19 the latter will, under action of the spring 18, be forced outwards to lock the striker block. In order to ensure that the pawl actually does look the striker block the recess 13 is bounded at its rear by the bevel or inclined surface 15 which, by hearing against the inner edge of the nose 19 of the pawl, forces the latter outwards.

The striker block 11 is now again locked and this condition lasts until it has again passed the tool 4, in which position the rear end 20 of pawl 16 again meets the stop 22 which causes the said pawl 16 to be again tripped in such a manner that its nose 19 releases the lug 14 on the striker block. The latter then, under action of the centrifugal force is again flung out into striking position.

These operations are repeated as long as the operator holds the lever 30 depressed.

When the operator lets go this lever, the spring 27 will turn the lever 25 in such a manner that the body 23 is moved to the left (Fig. 1). This removes the stop 22 from the path of the pawl 16,- and the latter willkeep the striker block 11 permanently locked, until the operator depresses the lever 30 and thereby restarts the hammer.

When the striker block isin locked position as shown in Fig. 4, the center of ravity common to body 6 and the striker b ock 11 will lie in the axis of revolution so that the hammer is quitefree from vibration caused by the centrifugal force.

The invention can be employed in other constructional forms than the one shown in the drawing and the arrangements of details shown may be replaced by other arrangements adapted to produce the same or similar effect. This applies not only to the shape of the striker block and the locking device which serves to arrest the same, after the impact has taken place, but also to the releasing device. I claim: 1. A mechanical hammer comprising a cas ing, a revoluble body, a striker block pivotally connected to said body and arranged under the influence of centrifugal force to be flung against a tool at every revolution of said body, a locking device associated with said body and arranged! to automatically catch and retain the striker block as the latter rebounds from impact on the tool, a stop adjustable but not rotatable in relation to the casing of the hammer, and arranged to automatically release the striker block when the latter has passed the tool.

2. A hammer as set forth in'claim 1, in which the center of gravity common to the body and the striking block after these two members have been locked together is situated on the axis of rotation of said body.

3. A hammer as set forth in claim 1, including means for positioning the adjustable stop, so that the locking device can be automatically withdrawn when the striker block is required to deliver a blow on the tool.

4. A hammer as claimed in claim 1, in which the locking device consists in a double armed pawl which is pivotally mounted in the body and one arm of which cooperates with a stop on a movable member, said stop being brought into the path of said arm at a predetermined point in each revolution of the body and automatically releases the striker block so that the latter, under action of centrifugal force, can fiy out into the striking position.

5. A hammer as claimed in claim 1, in which the striker block has a lug which engages behind the locking device opposite an inclined surface with which the striker block is provided and which, when the striker block rebounds, comes into contact with the inner edge ofthe locking device and positively ensures the locking of the striker block to the revoluble body.

6. A hammer as claimed in claim 1, in which the locking device consists in a double armed pawl which is pivotally mounted in the body and one arm of which cooperates with a stop on a movable member, saidstop being brought into the path 'of said arm at a pgedetermined point in each revolution of the dy and automatically releases the striker block so that the latter, under action of centrifugal force, can fly out into the striking position, in which the hammer has a handle provided with a recess and a pivoted lever 1n said recess,- and also includln a double armed lever disposed in the casing of the hammer to which motion is communicated by said pivoted lever, one end of said double armed lever being engageable with the said stop, so that by pressure upon the said pivoted lever said stop can be pushed into the path of the said locking device.

In witness whereof he affixes his signature.

HERMAN NIELSEN. 

